Abstract A premature failure that occurs before the expected load cycle during the torsional fatigue test of a propeller shaft assembly prototype is studied. In these test crack mainly originated repetitively from one of the components, namely Flange yoke at same region. To determine the root reason of the failure a detail CAD model of Flange yoke was developed and analyzed by Finite Element Method. Fatigue crack initiation and location were determined and compared with test data. We found good correlation between FEM results with testing failure results. Design improvements solutions are proposed to increase the fatigue life. Mechanical properties of the Flange yoke were determined by the tensile strength test. Using these input datas stress and strain analysis was performed in ANSYS software. Keywords: Finite Element Analysis, Stress Concentration, Structural Analysis

1. IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308
_______________________________________________________________________________________
Volume: 04 Issue: 02 | Feb-2015, Available @ http://www.ijret.org 747
FAILURE PREDICTION OF PROPELLER-SHAFT PROTOTYPE USING
FINITE ELEMENT ANALYSIS
R. K Praharaj1
, N. Gadre2
, A. Maharathy3
1
Mechanical Engineering Dept. NIT, Rourkela, India
2
Mechanical Engineering Dept. VJTI, Mumbai, India
3
Mechanical Engineering Dept. IIT,Bhubaneswar, India
Abstract
A premature failure that occurs before the expected load cycle during the torsional fatigue test of a propeller shaft assembly
prototype is studied. In these test crack mainly originated repetitively from one of the components, namely Flange yoke at same
region. To determine the root reason of the failure a detail CAD model of Flange yoke was developed and analyzed by Finite
Element Method. Fatigue crack initiation and location were determined and compared with test data. We found good correlation
between FEM results with testing failure results. Design improvements solutions are proposed to increase the fatigue life.
Mechanical properties of the Flange yoke were determined by the tensile strength test. Using these input datas stress and strain
analysis was performed in ANSYS software.
Keywords: Finite Element Analysis, Stress Concentration, Structural Analysis
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1. INTRODUCTION
A drive shaft or propeller shaft is a mechanical component
which is used for transmitting power from the gear box to
the differential in the vehicle. Propeller shaft is used as a
connector between gearbox and differential as they are
cannot be connected directly because of their position in the
vehicle and also they need a relative motion between them.
High torque is transmitted through the propeller shaft, so it
is subjected to high torsion and shear stress, therefore
propeller shafts should strong enough to bear these stresses
also as it is a rotating component additional weight leads to
increase mass moment of inertia. Generally propeller shaft
assembly as shown in fig. 1 consists of many components,
namely flange yoke, short fork, long fork, rear housing,
universal joint cross and tube. Therefore a failure of one of
the components leads to propeller shaft failure. Thus, all the
components should bear the resisting torque independently.
As per acceptance criteria, the propeller shaft should resist
1×10^5 cycles without any failure, but it is observed that
cycles before fatigue failure was about 1.6X10^4.
To predict the root reasons of earlier failure of flange yoke,
a detailed 3D model of flange yoke was developed in CREO
version 2 software. Finite element analysis was carried out
on that model. The stress and strain analysis were carried
out in ANSYS WORKBENCH V14.5. By this analysis
induced high stress regions were obtained.
Fig.1 Propeller shaft assembly

2. IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308
_______________________________________________________________________________________
Volume: 04 Issue: 02 | Feb-2015, Available @ http://www.ijret.org 748
2. PROBLEM DEFINATION
This prototype propeller shaft was supposed to be designed
for 5250 Nm transmitting torque for transport commercial
vehicles. During the validation, it was noticed that after
16,000 cycles, propeller shaft failed as shown in fig. 2. Only
flange yoke component was broken during the testing as
shown in fig. 3. There were three propeller shaft assembly
were tested for validation but all propeller shafts were failed
below 20000 cycles with similar failure pattern i.e in all
cases flange yoke was failed. Crack initiation pattern were
same for all the flange yoke. Scope of this study was to find
the root cause behind the failure and to propose alternative
way to avoid that failure.
Fig.2 Failure snap of Propeller shaft
Fig.3 Failure snap of Flange yoke
3. FINITE ELEMENT ANALYSIS
A full scaled CAD model of flange yoke was prepared for
the analysis as shown in fig 4. And imported to ANSYS
WORKBENCH for constituting a FE model. To build the
Finite Element Model, Flange yoke was meshed using solid
92, a higher order three dimensional solid element, which is
suitable for the meshing irregular shape model. Solid 92
element has 10 nodes having three translational DOF at each
node [2]. At critical region, finer meshing was done for
better results. Finite Element model consisted of 103839
elements and 160311 nodes. Mechanical properties of the
material as shown in below table1 were taken for static
structural analysis.
Table1: Physical properties of 35C8
Material Young's Modulus, E (GPA ) Poisson’s ratio, µ Yield strength, Syt (MPa) Ultimate Strength, Sut (MPa)
35C8 210 0.3 650 850
3.1 Loading and Bounadary Condition
Loading and boundary condition applied to the flange yoke
is shown in fig. 5 Here torque is applied to the mass node,
which is connected to eye fork surface through the rigid
elements. As this component is going to held by serration
engagement with mating parts, so that restraint these
engaged serrations faces only which resist the applied torque
also it has to be restrained at the bolt sitting hole for axial
movement where it is bolted with mating parts.
Fig. 4 CAD model of Flange yoke

3. IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308
_______________________________________________________________________________________
Volume: 04 Issue: 02 | Feb-2015, Available @ http://www.ijret.org 749
Fig. 5 loading and boundary condition applied on the FE
model
3.2 Result Interpitation
From the Von-mises stress plot as shown in fig. 6, it is
clearly seen that relatively high stress is induced at a bolt
mounting area which promotes to crack initiation. We found
that while testing, cracking was started from the bolt sitting
region. Fig.8 shows the total displacement of flange yoke
during loading. Fig.9. shows that the factor of safety
distribution in the flange yoke and it is clearly seen that at
the critical region factor of safety is close to zero, thus that
region enhance to crack initiation.
Fig. 6 shows von mises stress plot
Fig.7 Shows zoom view A
Fig.8 Shows total displacement plot
Fig. 9. Factor of safety distribution

4. IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308
_______________________________________________________________________________________
Volume: 04 Issue: 02 | Feb-2015, Available @ http://www.ijret.org 750
4. RESULTS AND DISCUSSION
FE analysis showed that the regions from which fatigue
failure was initiated during the fatigue torsional test, are
subjected to the stress concentration, which can cause a
premature failure before the acceptance criteria of 1x 10^5
cycles. At the critical region, stress (620 MPa) was closed to
the yield strength of the specified material also factor of
safety close to zero. Critical regions which obtained in FE
analysis are well agreeing with torsional test result. Increase
of the fatigue life is dependent on the decrease in stress
concentration. One of the easy way to reduce stress
concentration and improve the fatigue life is adding material
to increase the thickness of the rib at the bolting area. A
proper fillet radius should give at that sharp transition zone,
which can reduce stress concentration factor.
5. CONCLUSION
Premature fatigue failure of propeller shaft was investigated
by using Finite Element Analysis. In this analysis torsional
torque test was simulated. The stress concentration region
was predicted at bolting sharp transition area. The region
from which crack originated were well matched with the
Finite Element Analysis results, thus by FE method the
location of failure can be predicted.
In order to fix the problem, redesign is required in the
critical region, increase the thickness of the rib at the bolting
area and proper fillet radius should give to reduce stress
concentration to obtain a longer fatigue life.
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